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1.
A person who sniffs the penis of his/her significant other for fidelity verification.

**This is a "red flag" for lack of trust in a relationshp.

1. Maria tired of always asking Joe where he'd been every time he came home late. She became a "penis sniffer" to confirm her suspicions that Joe was cheating on her. (She also suspected that it Veronica from the accounting department, but first thing first.)
by nycapbarista February 28, 2009
 
2.
A term of insult to claim that someone sniffs penises. Better used towards males.
"John you're such a freaking penis sniffer!"
by dei June 17, 2006